A control system of the general type described above is disclosed in German Patent (OLS) No. 3,434,780 which is concerned with a device for single feed of bills of currency from a container provided in an automatic money changer. Devices of this type must operate reliably and accurately, and optimum regulation of the pressing force exerted by the pressing device on a stack of currency bills in the container and thus on the draw-off roller system is of crucial importance. With the known control system, the output force of an electric drive motor is regulated, and the drive motor presses a pressure plate against the stack of currency notes in the money holder so the stack of bills is pressed with a given pressing force against the draw-off roller system. This pressing force is measured and is supplied as the actual value to the control circuit.
In this way, the pressing force can be regulated relatively accurately in accordance with a control value as an input value, but such a control value must be determined experimentally and then must always be supplied consistently to the control circuit for certain types and sizes of sheets.
Such a control system functions satisfactorily in draw-off of sheet material whose properties are largely constant within a stack of sheets, i.e., when processing new sheets that are free of folds and are of a uniform quality. In dispensing devices for paper currency, however, such optimum conditions cannot be expected and so the control value used for the type of control system known in the past is never optimum for each individual stack of paper currency, so errors in feed that can be attributed to too little or too much pressure against the draw-off roller system are unavoidable.